let u: undefined = undefined;
let n: null = null;

// null和undefined赋值给string
let str:string = "666";
str = null
str= undefined

// null和undefined赋值给number
let num:number = 666;
num = null
num= undefined

// null和undefined赋值给object
let obj:object ={};
obj = null
obj= undefined

// null和undefined赋值给Symbol
let sym: symbol = Symbol("me");
sym = null
sym= undefined

// null和undefined赋值给boolean
let b1: boolean = false;
b1 = null
b1= undefined

// null和undefined赋值给bigint
let big: bigint;
big = null
big= undefined




